Zeolites are crystalline aluminosilicate compositions which are microporous and which are formed from corner sharing AlO2 and SiO2 tetrahedra. Numerous zeolites, both naturally occurring and synthetically prepared, are used in various industrial processes. Synthetic zeolites are prepared via hydrothermal synthesis employing suitable sources of Si, Al and structure directing agents such as alkali metals, alkaline earth metals, amines, or organoammonium cations. The structure directing agents reside in the pores of the zeolite and are largely responsible for the particular structure that is ultimately formed. These species balance the framework charge associated with aluminum and can also serve as space fillers. Zeolites are characterized by having pore openings of uniform dimensions, having a significant ion exchange capacity, and being capable of reversibly desorbing an adsorbed phase which is dispersed throughout the internal voids of the crystal without significantly displacing any atoms which make up the permanent zeolite crystal structure. Topological zeolite structures are described in Atlas of Zeolite Framework Types, which is maintained by the International Zeolite Association Structure Commission at http://www.iza-structure.org/databases/. Zeolites can be used as catalysts for hydrocarbon conversion reactions, which can take place on outside surfaces as well as on internal surfaces within the pore.
The alkylation of aromatic hydrocarbons such as benzene with light olefins such as ethylene and propylene is a very important process in a petrochemical refinery. The production of ethylbenzene is used to provide a feedstock for styrene production, while alkylation of benzene with propylene produces isopropylbenzene (cumene). Cumene is an important feedstock to make phenol as well as a good gasoline blending component. These alkylation processes typically use a catalyst composed of one of or a combination of 12-ring and 10-ring zeolites structure types such as FAU, BEA, MWW, and MFI to enable high conversion and high selectivity to alkylated benzenes. In all these alkylation processes, new catalysts are continuously needed with high overall conversion of the feedstock and good selectivity to alkylated benzenes.
Especially advantageous would be a commercially utilizable catalyst containing 12-membered rings and 10-membered rings in the same 3-dimensional structure. Commercial utility is typically seen in aluminosilicate structures which are synthesized in hydroxide media with readily available structure directing agents. Zeolites which contain both 12-membered and 10-membered rings in 3-dimensional structures belong to the CON, DFO, IWR, IWW and MSE structure types. The synthesis of CIT-1, a zeolite of the CON structure type, is described in U.S. Pat. No. 5,512,267 and in J. Am. Chem. Soc. 1995, 117, 3766-79 as a borosilicate form. After synthesis, a subsequent step can be undertaken to allow substitution of Al for B. The zeolites SSZ-26 and SSZ-33, also of the CON structure type are described in U.S. Pat. No. 4,910,006 and U.S. Pat. No. 4,963,337 respectively. SSZ-33 is also described as a borosilicate. All 3 members of the CON structure type use very complicated, difficult to synthesize structure directing agents which make commercial utilization difficult. The known member of the DFO structure type is DAF-1 which is described as an aluminophosphate in Chem. Commun. 1993, 633-35 and in Chem. Mater. 1999, 11, 158-63. Zeolites from the IWR and IWW structure types are synthesized only in hydrofluoric acid containing synthesis routes, making commercial utilization difficult.
One particular zeolite of the MSE structure type, designated MCM-68, was disclosed by Calabro et al. in 1999 (U.S. Pat. No. 6,049,018). This patent describes the synthesis of MCM-68 from dication directing agents, N,N,N′,N′-tetraalkylbicyclo[2.2.2]oct-7-ene-2R,3S:5R,6S-dipyrrolidinium dication, and N,N,N′,N′-tetraalkylbicyclo[2.2.2]octane-2R,3S:5R,6S-dipyrrolidinium dication. MCM-68 was found to have at least one channel system in which each channel is defined by a 12-membered ring of tetrahedrally coordinated atoms and at least two further independent channel systems in which each channel is defined by a 10-membered ring of tetrahedrally coordinated atoms wherein the number of unique 10-membered ring channels is twice the number of 12-membered ring channels.
Applicants have successfully prepared a new family of materials designated UZM-35. The topology of the materials is similar to that observed for MCM-68. The materials are prepared via the use of simple, commercially available structure directing agents, such as dimethyldipropylammonium hydroxide, in concert with small amounts of K+ and Na+ together using the Charge Density Mismatch Approach to zeolite synthesis (U.S. Pat. No. 7,578,993).
The alkylation of benzene with ethylene can be performed in gas phase conditions where all the reactants are in the gaseous phase while passing over the solid catalyst or in liquid phase conditions where at least the benzene is present in the liquid phase while passing over the solid catalyst. The UZM-35 family of materials is capable of catalyzing the alkylation of benzene with ethylene in either commercially relevant condition.
The UZM-35 family of materials is able to provide and maintain high conversion of propylene and high selectivity to isopropylbenzene during alkylation of benzene with propylene due to its particular pore geometry and framework Si/Al ratio. The UZM-35 zeolite contains significant amounts of Al in the tetrahedral framework, with the mole ratio of Si/Al ranging from about 2 to about 12.